1. Technical Field
The invention relates to air spring assemblies for vehicle suspensions, and in particular to an air spring having an auxiliary reservoir interchangeably mounted thereon to provide a variable spring rate to the air spring by increasing the total volume of the pressurized fluid by the auxiliary reservoir chamber.
2. Background Information
Air spring assemblies typically include two end plates or bead plates, or one end plate and a piston, which are sealingly connected to respective ends of a hollow fabric reinforced rubber sleeve or bladder. These air springs are used primarily for implementation in motor vehicles for supporting the vehicle body or for use in other types of equipment subject to shock to provide cushioning therefor. The air springs are sealed at the ends to form a pressurized fluid chamber within the bladder. The air spring will generate a certain load at a given height and pressure, and upon the air spring experiencing a road displacement input, the sleeve will begin to collapse or extend as the end members move toward or away from each other respectively, to yield predictable dynamic load characteristics.
These dynamic load characteristics of the air spring are a function of the internal air pressure, volume and effective area. One of the factors which determines the spring rate is the volume of air contained within the flexible sleeve or bladder of the air spring. Varying this volume of air enables various spring rates to be achieved. This is presently accomplished by various means such as by supplying or removing air into or from the air spring chamber through various control valves and by the use of auxiliary air reservoirs which are fluidly connected to the vehicle air spring. Thus changing the spring rate of an existing air spring enables the same air spring to provide certain desired characteristics for the vehicle. The smaller the volume of the air chamber the firmer will be the ride provided thereby.
Heretofore auxiliary reservoirs for air springs usually consisted of a remotely mounted reservoir, which was connected by a hose or other fluid communication lines to the air chamber of the air spring. These remotely located reservoirs generally contained various means for adjusting the volume of the air within the air chamber. These auxiliary reservoirs are located remote from the air spring and are not formed as an integral part thereof, and the size and length of the connecting fluid lines often retard the air flow reducing the effectiveness of the change of volume. Other types of auxiliary reservoirs are connected to an existing air spring by complicated control valves, which could be subject to maintenance problems.
Often it is desirable to tailor the dynamic load characteristics of the air spring to fit a particular vehicle or application. However, it is not always practical to change the bladder size of the air spring for all applications and some vehicles have certain space limitations which do not allow for a larger bladder size and have restrictions on the height and width of the air spring.
What the art needs is an air spring assembly which allows for control of its overall effective air chamber volume in order to achieve certain dynamic load characteristics without having to change the physical side of the bladder of the existing air spring by selectively adding an auxiliary reservoir to the air spring, wherein the air chamber of the auxiliary reservoir is fluidly connected with the internal chamber of the air spring.
Another aspect of the invention is to provide an annular elastomeric seal surrounding a fluid passage between the auxiliary reservoir and air spring chamber which is located between an outer surface of the bead plate and end wall of auxiliary reservoir, which components are in abutting contact, to provide an air seal to prevent the escape of air from the internal chambers.
Still another aspect of the invention is to use the existing bead plate of the air spring which is modified by forming an enlarged central opening, in which an internally threaded insert is secured for threadably receiving an externally threaded coupler extending outwardly from an end wall of the auxiliary air chamber. This enables the auxiliary air chamber to be threadably engaged and secured on the bead plate of the existing air spring wherein the auxiliary reservoir can have various bladder sizes, axial lengths and configurations depending upon the particular application in which the combination air spring and auxiliary reservoir is adapted for use.
A further feature of the invention is by having an auxiliary reservoir directly mounted on the air spring end plate, it enables a small volume air spring to be used in an environment where larger diameter air springs with already low spring rates, would be prohibited.
Another advantage of the air spring assembly of the present invention is that the auxiliary reservoir can be interchangeable as to height and diameter, but maintain a large diameter common orifice extending between the auxiliary reservoir and air spring with a relatively short fluid path therebetween, to allow for the rapid transfer of large volumes of air between the air chambers.
The air spring assembly of the present invention enables existing bead plates to be utilized wherein an enlarged opening is formed in the center of the bead plate and an internally threaded insert is secured by brazing, welding or other securement means, with the auxiliary reservoir, regardless of its size and configuration, all having an externally threaded male coupler which screws into the air spring and seats against an outer O-ring located in an annular groove formed in the insert of the air spring, to provide for an airtight and compact air spring assembly.
Still another feature of the invention is to enable the end wall of the auxiliary reservoir which is located opposite of the end wall having the externally threaded coupler, to have the same mounting stud and air duct inlet opening arrangement as heretofore formed in the end member of the air spring enabling the auxiliary reservoir to be secured in and to the existing mounting holes and/or brackets on the vehicle as was the existing end member of the air spring, eliminating any modifications to the vehicle on which the combination auxiliary reservoir and air spring is mounted.